US President Barack Obama said on Friday that America's history of racial discrimination had contributed to a persistent economic gap between blacks and whites in the 50 years since Martin Luther King's landmark "I have a dream" speech.

Obama said his own story showed the "enormous strides" the United States had made since King's speech, but as Washington commemorates the anniversary of King's address, the disparity between black and white income remained.

"What we've also seen is that the legacy of discrimination, slavery, Jim Crow, has meant that some of the institutional barriers for success for a lot of groups still exist," Obama, the first black US president, said in answering a question at a town hall meeting at Binghamton University in New York state.

"You know, African-American poverty in this country is still significantly higher than other groups. Same is true for Latinos. Same is true for Native Americans," he said.

Divisive US politics is a factor in the growing gap between rich and poor in America, Obama said.

"The tendency to suggest somehow that government is taking something from you and giving it to somebody else and your problems will be solved if we just ignore them or don't help them ... is something that we have to constantly struggle against, whether we're black or white or whatever color we are," he said.

Data shows that five decades after King's speech during the "March for Jobs and Freedom" in Washington on Aug. 28, 1963, the black-white economic gap has persisted despite huge gains in education and political clout by blacks.

Black unemployment is about twice that for whites, the same as in 1963. Blacks also have been disproportionately hammered by the deep 2007-2009 recession and credit crunch.

Heidi Shierholz, a labor economist at the Economic Policy Institute in Washington, said blacks lagged whites for a number of reasons. They include slightly lower levels of education, weaker business networking and the US failure to create good-paying jobs since the 1970s.

But discrimination also plays a role, she said. Studies have shown, for example, that on identical job applications those with white-sounding names are more likely to get callbacks than those with black-sounding names.

Such studies "show that discrimination is still alive and well," she said.

In 1963, the jobless rate among blacks was 10.9%, more than twice that for whites, according to the Economic Policy Institute.

Last month, black unemployment was 12.6%, compared with 6.6% for whites, the labor department said.

The income gap between black and white families has narrowed somewhat in the last half century.

Black families on average had incomes in 2011 that were two-thirds that of whites, up from 57% in 1963, Census Bureau data shows. The poverty rate for blacks has dropped, to 28% in 2011 from 42% in 1966.

Household income

Census Bureau numbers show that since the recession started in 2007, average black household income has fallen 12.4%, compared with a 7% drop for whites.

Stuart Butler, director of the Center for Policy Innovation at the Heritage Foundation in Washington, said black economic achievement was hampered by such factors as a high rate of out-of-wedlock births, low savings rates, poor schools and a high rate of incarceration for black men.

With all of those in place, "it's just devastating for economic improvement," he said.

The economic gap between the races has remained nearly unchanged even as blacks have made big gains in education and political representation.

The percentage of blacks who graduate from high school has risen more than threefold, to 85% last year. There are more than 10 times as many black college students now than there were 50 years ago, according to the Census Bureau.

Political gains are just as marked. There were 10,500 black elected officials in 2011, a 10-fold increase from 1970, the first year the number was compiled, Census data showed.

The current Congress has 45 black representatives, up from five in 1963, according to the House historian's website. There is one black U.S. senator, Republican Tim Scott of South Carolina, and there were none in 1963.